Breast Cancer is the most common malignancy in women in the Western world and every year about 200,000 women are diagnosed with breast cancer in the US and more than 40,000 die from this disease (www.cdc.gov). Despite the fact that combination chemotherapy regimens elicit a 50-70% objective response rate in patients with metastatic breast carcinoma less than 20% of patients achieve durable complete remission (Esteva F J, et al. J Clin Oncol 2002: 20:1800-8). The major reason for patient death is due to metastasis and resistance to current therapies including chemotherapy, hormonal therapy and radiation (Polychemotherapy for early breast cancer: an overview of the randomised trials. Early Breast Cancer Trialists' Collaborative Group. Lancet 1998: 352:930-42.). Thus, the development of novel targeted therapeutic strategies is urgently needed to enhance the efficacy of current therapies and prolong patient survival.
Calmodulin-dependent protein Kinase-III (CaMK-III) a.k.a. Eukaryotic elongation factor 2 kinase (eEF-2K) is an unusual calcium/calmodulin (Ca/CaM)-dependent Ser/Thr-kinase that is activated by mitotic agents involved in cell proliferation and viability (Parmer T G, et al. Br J Cancer 1999: 79:59-64). CaMK-III was originally identified as a Ca2+/CaM dependent protein kinase (Nairn A C, et al. Proc Natl Acad Sci USA 1985: 82:7939-43). It is highly regulated by second messengers (e.g. Ca2+, PIP3), as well as by a number of different protein kinases. Upon mitogenic stimulation there is a rapid activation of CaMK-III, which leads to the subsequent phosphorylation of elongation factor 2 (eEF2), which regulates elongation of protein synthesis (Parmer T G, et al. Cell Growth Differ 1997: 8:327-34).
CaMK-III activity has been found to be significantly increased in breast cancer specimens but absent in normal tissue adjacent to breast cancer (Chafouleas J G, et al. Proc Natl Acad Sci USA 1981: 78:996-1000). Increased activity of this kinase has been reported in proliferating cells (e.g. malignant glioma cells (Bagaglio D M, Hait W N. Cell Growth Differ 1994: 5:1403-8), and HL60 leukemia cells (Nilsson A, Nygard O. Biochim Biophys Acta 1995: 1268:263-8)), but is reported to be absent in nonproliferating cells (Parmer T G, et al. Cell Growth Differ 1997: 8:327-34). In breast cancer cells, the activity of CaMK-III is stimulated by mitogens and growth factors (Parmer T G, et al. Activity and regulation by growth factors of calmodulin-dependent protein kinase III (elongation factor 2-kinase) in human breast cancer. Br J Cancer 1999: 79:59-64). Progression through the G1-phase of the cell cycle and entry into the S phase (the G1/S transition) requires the activity of CaMK-III, which is mediated by a rise in intracellular calcium (Ca2+), and/or the up-regulation of c-AMP (Proud C G. Biochem J2007: 403:217-34). Hypoxia, nutrient deprivation and metabolic stress stimulate CaMK-III through activation of AMPK, leading to the phosphorylation of eEF2 and the inhibition of protein synthesis (Browne G J, et al. J Biol Chem 2004: 279:12220-31).
Serotonin (5-hydroxytryptamine, 5-HT), a monoamine neurotransmitter, is a critical local regulator of epithelial homeostasis in the breast and other organs. Serotonin exerts its actions through a repertoire of 15 or more receptor proteins, belonging to seven discreet families. Six of the families of 5-HT receptors are G-protein-coupled, including Gi: 5-HT1, Gs: 5-HT4,6,7, and Gq/11: 5-HT2,5. 5-HT3 is uniquely a ligand-gated cation channel, related to the nicotinic acetylcholine receptor. Previous studies suggest that serotonin, plays a mitogenic role in cancer cells including bladder, pancreatic, prostate hepatocellular cancers, small cell lung carcinoma cells [Parmer T G, et al. Br J Cancer 1999: 79:59-64, Nairn A C, et al. Proc Natl Acad Sci USA 1985: 82:7939-43, Parmer T G, et al. Cell Growth Differ 1997: 8:327-34, Chafouleas J G, et al. Proc Natl Acad Sci USA 1981: 78:996-1000, Bagaglio D M, Hait W N. Cell Growth Differ 1994: 5:1403-8, Nilsson A, Nygard O. Biochim Biophys Acta 1995: 1268:263-8] and breast cancer (Sonier et al., 2006). Among the 5-HT receptors, the 5-HTR2B has been described to mediate proliferation [Proud C G. Biochem J2007: 403:217-34, Browne G J, et al. J Biol Chem 2004: 279:12220-31, Franken N A, et al. Nat Protoc 2006: 1:2315-9] and recently, 5-HTR2A signaling has been shown to promote mitogenic signal in MCF7 breast cancer cells [Lu K P, Means A R. Endocr Rev 1993: 14:40-58]. It has been reported that complex alterations in the intrinsic mammary gland serotonin system of human breast cancers exist [Liao D J, Dickson R B. Endocr Relat Cancer 2000: 7:143-64]. Pai et al. demonstrated that in the normal mammary gland, 5-HT acts as a physiological regulator of lactation and involution, in part by favoring growth arrest and cell death. This tightly regulated 5-HT system is dysregulated in multiple ways in human breast cancers. Specifically, tyrosine hydroxylase, TPH1, (an enzyme found in peripheral tissues leads to production of serotonin and expressed in non neuronal tissues) expression increases during malignant progression. 5-HT receptor expression is dysregulated in human breast cancer cells, with increased expression of some isoforms and suppression of others. The receptor expression change is accompanied by altered downstream signaling of 5-HT receptors in human breast cancer cells, resulting in resistance to 5-HT-induced apoptosis, and stimulated proliferation. Pai et al found that HT1D, 1F, 2C and 3A are expressed in some breast cancer cells compared to MCF10A normal breast epithelium [Liao D J, Dickson R B. Endocr Relat Cancer 2000: 7:143-64].
Apoptosis (programmed cell death type I) and autophagic cell death (programmed cell death type II) are crucial physiological mechanisms that control the development, homeostasis, and elimination of unwanted and malignant cells [Musgrove E A. Growth Factors 2006: 24:13-9]. It is now evident that elimination of cancer cells following chemotherapy treatment occurs, in part, via the induction of autophagic cell death [Abukhdeir A M, Park B H. Expert Rev Mol Med 2008; 10:e19, Ozpolat B, Mol Cancer Res 2007: 5:95-108, Shaw L M. Methods Mol Biol 2005: 294:97-105], Autophagic cell death or type II programmed cell death is a form of non-apoptotic cell death that can be induced by different conditions including serum starvation, gamma-radiation, toxic stimuli, and chemotherapy [Musgrove E A. Growth Factors 2006: 24:13-9].
Autophagy is characterized by an increase in the number of autophagosomes, vesicles that surround such cellular organelles as Golgi complexes, polyribosomes, and the endoplasmic reticulum [Finn R S. Ann Oncol 2008: 19:1379-86]. Subsequently, autophagosomes merge with lysosomes and digest the organelles, leading to cell death. In contrast to apoptosis, autophagic cell death does not involve classic DNA laddering. A growing body of evidence suggests that alterations in the pathways regulating autophagic cell death may result in cancer development. Provided herein are methods and compositions addressing these and other needs in the art.